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If there was no balance issue with the wing forward then there would be more leverage since the tail was farther away from the wing. But I believe the wing was moved back for balance with the extended tail. Hope this helps.And that was a proposed intercooler? I'm curious if a belly radiator of some sort or two ventral radiators like the Spitfire would be workable
So it was further back? On a fighter it'd be under the pilot more or less?
What about the fact that the control linkages would be easier to lay out because of the fact that you don't have any interruptions in the fuselage because of the doors? They just ran them under the doors back to the engine.
There was supposedly a proposal for some kind of higher altitude V-1710 that got cancelled, I'd almost swear I remember hearing that with the P-39. Was this a single stage supercharger with a different gear ratio or a twin-speed set-up? Or was it twin-speed? Maybe the V-1710-59, first attempt at increasing the supercharger gear ratio to 9.6? Unsuccessful because of excessive wear to the supercharger gears. Redesign for wider gears resulted in the successful -83 from August '42.
BTW: While I'm beating a dead horse, I remembered something you stated about the P-63 -- it's wing was moved back by a foot. The changes needed to mount the twin-stage supercharger added some weight and that's why some tankage was moved around and, while a turbocharger would be bulkier and heavier -- if the wings stayed forward by their normal amount, that would mean the space between the wing and the elevator would be much larger, and the wing seems to bear a significant amount of the aircraft's weight, and while I could definitely be wrong, would you be able to have enough leverage to make everything work?
P-39 was too small for a turbo, much less two. See above for more answers.P-39 Expert
1. Would the control cables be lighter if they didn't have to be run under the doors? I figure the more changes in direction would make the cables longer and that would add some weight. Frankly -- I'm not even sure why they added the doors to the design. Me either, but they stayed with the plane even through the upgrade to the P-63.
2. The V-1710-59 and -83: Were they single-speed or twin-speed? What full-throttle height were they expected to reach? Also, was there anyway for them to have known, reasonably speaking, that the gears would wear-down more easily and would need to be beefed up to work? Both single speed, Allison never develped a two speed. FTH was about 15000', up from 12000' with the earlier 8.8 geared engines. Allison was hoping for the step up gears to be interchangeable from 8.1 (for two stage engines) to 8.8 (earlier altitude rated engines) to 9.6 (later altitude rated engines) but the load on the gears was too high at 9.6. This was a big disappointment as the earlier -59 engines were tested in late '41 but the redesign pushed them back to mid-late '42, almost a year later.
3. I thought you said the P-63 was lengthened because the wing was moved back about a foot, and then to give the tail adequate leverage, the longer fuselage gave the tail adequate leverage? Yes.
I would have figured
Would it have been acceptable to use two smaller turbochargers in lieu of one? It might sound silly but from what I remember the F6F prototypes used such a set-up. I'm not sure if they would have viewed that as acceptable either as a fix or a start.
- P-63
- If the wing was moved rear-words, the C/L would also go back accordingly and
- This would produce a stronger nose-down tendency, and need more elevator to provide level flight and maneuvering
- Making the plane longer and with the elevator further back and you'd get adequate control The wing was moved because the C/G changed, not vice versa.
- P-39
- The P-39 had the wing forward by a foot and thus these problems didn't exist C/L and C/G need to be in the same place or plane is out of balance.
- A turbocharger mounted behind the engine would be somewhat heavier and possibly further back than the P-63's set-up which would make the plane tail-heavy Yes.
- Admittedly a longer tail would just make the plane twitcher... Should make it smoother instead of twitchier.
So I'm not the only one to think the car door idea was weird?Me either, but they stayed with the plane even through the upgrade to the P-63.
The P-39 had a little ram compression effects if I recall right?Both single speed, Allison never develped a two speed. FTH was about 15000', up from 12000' with the earlier 8.8 geared engines. Allison was hoping for the step up gears to be interchangeable from 8.1 (for two stage engines) to 8.8 (earlier altitude rated engines) to 9.6 (later altitude rated engines) but the load on the gears was too high at 9.6. This was a big disappointment as the earlier -59 engines were tested in late '41 but the redesign pushed them back to mid-late '42, almost a year later.
Okay, we're on the same page regarding lengthYes.
It might sound silly but two turbos running in parallel can be quite small compared to one normal turbo. It would allow the effect of one big turbo in a smaller place. That's why I mentioned it.P-39 was too small for a turbo, much less two.
Do you have any idea why?Allison did develop 2 speed supercharged versions of the V-1710, but none of these went into production.
Nice touch...Note that the 2 speed supercharged engines had (or would have had) a larger impeller of 10.25in, compared with 9.5in for the standard impeller. I believe that 10.25in also happens to be the impeller size used in most single stage Merlins.
The first supercharger I knew of to use axial-flow was Eastman Jakob's work. Do you know anymore about the Birman-type?The XF6F-2 used an experimental Birman type mixed flow turbocharger - which probably means it had axial and centrifugal compressors. Initially it was to have been fitted with the R-2600 (not sure if that ever flew), but was later fitted with the R-2800 connected to the turbocharger.
So I'm not the only one to think the car door idea was weird?
It might sound silly but two turbos running in parallel can be quite small compared to one normal turbo. It would allow the effect of one big turbo in a smaller place. That's why I mentioned it.
Do you have any idea why?
The first supercharger I knew of to use axial-flow was Eastman Jakob's work. Do you know anymore about the Birman-type?
Would it have been acceptable to use two smaller turbochargers in lieu of one? It might sound silly but from what I remember the F6F prototypes used such a set-up. I'm not sure if they would have viewed that as acceptable either as a fix or a start.
When were the superchargers you listed developed?No orders.
When were the superchargers you listed developed?
Like 1944 or 1945?Late in the war.
Like 1944 or 1945?
Why would you think the doors would require longer control cables ? The control stick yoke has connections in the floor right in front of the seat, like any other aircraft of that era, door or canopy hasn't got any effect on the length of the control cables.P-39 Expert
1. Would the control cables be lighter if they didn't have to be run under the doors? I figure the more changes in direction would make the cables longer and that would add some weight. Frankly -- I'm not even sure why they added the doors to the design..
Looking back on it, I don't actually know why I said what I did. I'm curious if any linkages ran along the sides? It seems that the aft sliding canopy would be more conventional and easier.Why would you think the doors would require longer control cables?
The P-39/P-63 had car doors because the cockpit framing provided structural support to the airframe.Looking back on it, I don't actually know why I said what I did. I'm curious if any linkages ran along the sides? It seems that the aft sliding canopy would be more conventional and easier.
I think the car doors were part of the turnover structure which was part of the framing. In my opinion it didn't need the turnover structure, just added weight that most other fighters didn't have. Without the turnover structure a bubble canopy could have been used eliminating the car doors and improving visibility. The framing wasn't really necessary for structure, the whole forward fuselage was based on the two longitudinal beams that ran from the nose to aft of the engine providing a very robust "canoe" that also kept the drive shaft straight. Altogether a good structural solution even without the turnover structure or framed canopy. Just my 2 cents worth.The P-39/P-63 had car doors because the cockpit framing provided structural support to the airframe.
I meant like 1944 late, or 1945 late. Depending on interpretation, either could be considered late.I can't even......
1. -35 was 11700'-12000' no ram without backfire screens. Critical altitude for the P-39D was 13800' with ram and no backfire screens per wwiiaircraftperformance.org.My questions...
- V-1710-35
- What's the engine critical altitude (no ram)?
- What's the aircraft critical altitude (ram) on the P-39D?
- V-1710-59
- What was the proposed engine critical altitude (no ram)?